More than 400 cyclists are fined or cautioned for failing to wear a helmet during South Australia police's Operation Safe Cycling, while only three drivers were cautioned for failing to keep a safe distance from cyclists.

Sixteen people are charged and the same number of vehicles seized across Melbourne during an operation targeting illegal street racing involving two groups who dub themselves the northern and southern 'skids'.

A man involved in a high speed chase, which ended in a serious crash in Adelaide's northern suburbs, was seen driving with his car bonnet over the windscreen and his head out of the driver's side window, police say.